Potential Form: Irregular Verbs (Suru and Kuru)

The potential form is all about possibility and ability. In English, we just add the word "can" before a verb. In Japanese, the verb itself changes its shape. For regular verbs, this is usually a predictable shift. But for our irregular friends, the change is a bit more dramatic. When you change suru or kuru into the potential form, you are signaling to the listener that an action is possible. It is not just about physical ability; it is also about circumstances. For example, "I can come" might mean "I have the time to come" or "I am allowed to come." Understanding this nuance makes your Japanese feel much more natural and less like a translated textbook.

1. 1Since these are irregular, there is no secret formula to calculate the change. You just have to memorize them. Luckily, there are only two!
2. 2Suru (to do) becomes Dekiru (can do).
3. 3Kuru (to come) becomes Korareru (can come).
4. 4Wait, did suru just turn into a completely different word? Yes, it did. Think of it like a Pokémon evolution. Suru evolves into Dekiru. You cannot say surareru to mean "can do." That is a different grammar point entirely! For kuru, the first sound changes from "ku" to "ko," and then we add "rareru."
5. 5Pro-tip: In modern casual Japanese, people often drop the "ra" in korareru and just say koreru. This is called "ra-nuki" (dropping 'ra'). It is super common with friends, but stick to korareru in formal writing or exams. It is like the difference between saying "I'm gonna" and "I am going to."

You will use these forms constantly in real-life scenarios.

• Scenario 1: Skills and Abilities. If someone asks if you can play tennis or speak Japanese, you use dekiru. "Nihongo ga dekiru" (I can do/speak Japanese) is a classic.
• Scenario 2: Availability. If a friend asks if you can come to their birthday bash on Friday, you would use korareru. "Kinyoubi ni korareru?" (Can you come on Friday?).
• Scenario 3: Compound Verbs. Many Japanese verbs are just a Noun + Suru (like benkyou suru for "to study"). To say "can study," you just swap suru for dekiru. So, benkyou dekiru.
• Scenario 4: Possibility. Use these when discussing if something is even possible. "Can we do this project by tomorrow?" would use the potential form of suru.

Don't use the potential form for things that happen naturally without effort. For example, you don't usually use the potential form for "to understand" (wakaru) because understanding isn't exactly a "skill" you turn on and off in the same way. Also, be careful with verbs of perception. "I can see" is usually mieru, not the potential form of "to look."

Another trap: Don't use the potential form when you are simply describing a future plan where ability isn't the focus. If you are definitely going to a party, just use the plain form. Only use the potential form if there is a question of whether you are *able* to make it happen. Think of it like a grammar traffic light; only turn it green when ability or permission is the main topic.

The biggest mistake learners make is trying to apply regular rules to these rebels.

• Mistake 1: Saying surareru. This sounds like you are being done by something (passive voice). It does not mean "can do."
• Mistake 2: Saying kurareru. This is also a passive form and sounds very strange if you mean "can come." Remember: ku changes to ko!
• Mistake 3: Using the particle wo with dekiru. While wo is becoming more common in casual speech, the gold standard for potential forms is the particle ga. Think of it as dekiru being a state of being able, rather than a direct action on an object.
• Mistake 4: Forgetting that dekiru is also a regular Group 2 (Ru-verb) once it has transformed. This means the negative is dekinai and the polite form is dekimasu.

You might have learned koto ga dekiru before. This is a more formal and slightly clunky way to say "can do." For example, taberu koto ga dekiru (I can eat). While this is grammatically correct, using the potential form directly is much more common in daily life.

Dekiru is also its own verb with other meanings! It can mean "to be made of," "to be finished," or "to be ready." If your mom yells "Gohan dekita yo!" she isn't saying the rice has the ability to do something; she is saying "Dinner is ready!" Context is your best friend here. Don't worry, you won't confuse a skilled tennis player with a bowl of rice... usually.